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91.
H2Bn- (n = 7—12) clusters are generated by laser vaporization of an isotopically enriched 11B target with helium containing 5% D2 as the carrier gas. 相似文献
92.
In our search for environmentally benign insecticides with high activity, low toxicity and low residue, a novel series of amides containing N-pyridylpyrazole moieties were designed and synthesized. The structures of the title compounds were characterized and confirmed by 1H-NMR and elemental analysis. Furthermore, the structure of compound 7l was determined by single crystal X-ray diffraction. The preliminary bioassay tests showed that some of them exhibited good insecticidal activities against Mythimna separata Walker, Plutella xylostella (Linnaeus, 1758) and Laphygma exigua Hübner. 相似文献
93.
波长为157nm的 O2 在受激准分子激光器作用下可离解为 O3P 和 O1D .为了在理论上研究化学反应 的量子干涉效应,利用一阶含时波恩近似及各向异性相互作用势建立了量子干涉效应模型,讨论了完全干涉和完全非干涉两种情况。 相似文献
94.
物质波的干涉是由于微观粒子具有波的特性而产生的干涉现象。对于双原子分子单三重混合态转动传能过程具有波动特性,两个通道间存在量子干涉效应。基于玻恩近似的微扰理论,本文利用各向异性相互作用势和直线轨迹近似给出了包含干涉相位角的干涉表达式,建立了新的量子干涉模型,并讨论了此模型中利用的近似理论。 相似文献
95.
Li WL Romanescu C Galeev TR Piazza ZA Boldyrev AI Wang LS 《Journal of the American Chemical Society》2012,134(1):165-168
We report the observation of two transition-metal-centered nine-atom boron rings, Rh?B(9)(-) and Ir?B(9)(-). These two doped-boron clusters are produced in a laser-vaporization supersonic molecular beam and characterized by photoelectron spectroscopy and ab initio calculations. Large HOMO-LUMO gaps are observed in the anion photoelectron spectra, suggesting that neutral Rh?B(9) and Ir?B(9) are highly stable, closed shell species. Theoretical calculations show that Rh?B(9) and Ir?B(9) are of D(9h) symmetry. Chemical bonding analyses reveal that these complexes are doubly aromatic, each with six completely delocalized π and σ electrons, which describe the bonding between the central metal atom and the boron ring. This work establishes firmly the metal-doped B rings as a new class of novel aromatic molecular wheels. 相似文献
96.
Dihydrogenated boron clusters, H(2)B(n)(-) (n = 7-12), were produced and characterized using photoelectron spectroscopy and computational chemistry to have ladderlike structures terminated by a hydrogen atom on each end. The two rows of boron atoms in the dihydrides are bonded by delocalized three-, four-, or five-center σ and π bonds. The π bonding patterns in these boron nanoladders bear similarities to those in conjugated alkenes: H(2)B(7)(-), H(2)B(8), and H(2)B(9)(-), each with two π bonds, are similar to butadiene, while H(2)B(10)(2-), H(2)B(11)(-), and H(2)B(12), each with three π bonds, are analogous to 1,3,5-hexatriene. The boron cluster dihydrides can thus be considered as polyene analogues, or "polyboroenes". Long polyboroenes with conjugated π bonds (analogous to polyacetylenes), which may form a new class of molecular wires, should exist. 相似文献
97.
Origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid
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We report on the investigation of the origin of high oxide to nitride polishing selectivity of ceria-based slurry in the presence of picolinic acid.The oxide to nitride removal selectivity of the ceria slurry with picolinic acid is as high as 76.6 in the chemical mechanical polishing.By using zeta potential analyzer,particle size analyzer,horizon profilometer,thermogravimetric analysis and Fourier transform infrared spectroscopy,the pre-and the post-polished wafer surfaces as well as the pre-and the post-used ceria-based slurries are compared.Possible mechanism of high oxide to nitride selectivity with using ceria-based slurry with picolinic acid is discussed. 相似文献
98.
The geometrical and electronic structures of nitrogen-doped β-SiC are investigated by employing the first principles of plane wave ultra-soft pseudo-potential technology based on density functional theory. The structures of SiC1-xNx (x = 0, 1/32, 1/16, 1/8, 1/4) with different doping concentrations are optimized. The results reveal that the band gap of β-SiC transforms from an indirect band gap to a direct band gap with band gap shrinkage after carbon atoms are replaced by nitrogen atoms. The Fermi level shifts from valence band top to conduction band by doping nitrogen in pure β-SiC, and the doped β-SiC becomes metallic. The degree of Fermi levels entering into the conduction band increases with the increment of doping concentration; however, the band gap becomes narrower. This is attributed to defects with negative electricity occurring in surrounding silicon atoms. With the increase of doping concentration, more residual electrons, more easily captured by the 3p orbit in the silicon atom, will be provided by nitrogen atoms to form more defects with negative electricity. 相似文献
99.
Electrically Pumped Room-Temperature Pulsed InGaAsP-Si Hybrid Lasers Based on Metal Bonding
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A pulsed InGaAsP-Si hybrid laser is fabricated using metal bonding. A novel structure in which the optical coupling and metal bonding areas are transversely separated is employed to integrate the silicon waveguide with an InGaAsP multi-quantum well distributed feedback structure. When electrically pumped at room temperature, the laser operates with a threshold current density of 2.9 kA/cm^2 and a slope efficiency of 0.02 W/A. The 1542nm laser output exits mainly from the Si waveguide. 相似文献
100.